To plot the path, you move dial "Plot" from 0 to 2 or animate the "Plot" channel. This moves actor "dummy" along the curve. "dummy" is just a moving little arrow so that you can see how the motion path looks like. In the end, you parent a more interesting prop or figure to actor "dummy" and hide "dummy" to animate the motion of the parented prop or figure. "Scale" scales the motion path. Higher "Scale" creates longer distances between the knots. "ScaleBits" scales the geometries of the knots and handles and preserves the distances. "ScaleBits" does not modify the shape of the motion path, it's only used to adjust the size of the bits in the scene when you are developing the path.